Technical Field
The present application relates to packaging of a semiconductor die and more particularly, to ring or coil patterned die pads of lead frames packages.
Description of the Related Art
Integrated circuits are formed from semiconductor dice that have been processed to form electronic circuitry. Before integrated circuits are put into commercial application, they are generally packaged in such a way to protect the semiconductor die. Integrated circuits are packaged in a variety of ways. A particularly common type of integrated circuit package is the lead frame.
FIGS. 1A and 1B are views of a known type of integrated circuit package 19. FIG. 1A is a top view of the integrated circuit package 19 including a lead frame 10. The frame includes a central die pad 12, tie bars 14, and wire bond leads 16. The dashed box denotes an integrated circuit die 18 positioned on the lead frame 10.
FIG. 1B is a cross-sectional view of the integrated circuit package 19 taken on cross-section lines 1B of FIG. 1A. The integrated circuit package 19 includes the integrated circuit die 18 positioned on the die pad 12 of the lead frame 10. The integrated circuit die 18 is coupled to the die pad by adhesive paste 24.
Molding compound 20 encapsulates the integrated circuit die 18 and the die pad 12. Bonding wires 22 electrically couple the wire bond leads 16 to the integrated circuit die 18.
It is common that a die pad of a lead frame is tooled to have a particular size relative to the integrated circuit die which will be placed thereon. This is because as a ratio of the die pad area to the integrated circuit die area increases, the likelihood of delamination of the molding compound from the lead frame also increases. If the molding compound becomes delaminated from the lead frame, the integrated circuit die within the package is at risk of being damaged. In particular, when the molding compound becomes delaminated from the die pad, moisture can seep into the integrated circuit package causing damage to the integrated circuit die or short-circuiting the bonding wires. If this happens, the integrated circuit die may function poorly or may cease functioning altogether. Furthermore, when delamination of the molding compound occurs, the integrated circuit die is more susceptible to damage from being bumped or jostled because the integrated circuit die is no longer fixed in place as securely as before delamination occurred.
Thus, great expense is incurred to tool a variety of lead frame die pad sizes to fit particular integrated circuit dies, even if the final packages are all the same size. To overcome this problem attempts have been made to include regular edge patterns for the die pad and dimples in the die pad in order to promote better adhesion of the molding compound to the die. However, these solutions have worked poorly and can be cost prohibitive.